The present invention relates to a polytrimethylene terephthalate fiber suitable for the high-speed draw false-twist texturing process and a method for producing the same. More specifically, the present invention relates to a partially oriented polytrimethylene terephthalate fiber capable of being subjected to the draw false-twist texturing process, in a stable manner and for a long period, and a method for production thereof.
A fiber using polytrimethylene terephthalate (hereinafter referred to as PTT) obtained from the polycondensation of terephthalic acid or a lower alcoholic ester of terephthalic acid; typically dimethyl terephthalate; with trimethylene glycol (1,3-propanediol) is an epoch-making fiber having properties similar to polyamide, such as a low elastic modulus (soft touch), excellent elastic recovery and a good dyeability as well as properties similar to polyethylene terephthalate (hereinafter referred to as PET), such as those excellent in resistance to light, heat settability and dimensional stability and a low water-absorption, and used for a BCF carpet, a brush, a tennis racket string or others (for example, see the U.S. Pat. Nos. 3,584,108 and 3,681,188, J. Polymer Science; Polymer Physics (Vol. 14, pages 263 to 274, Published in 1976), Chemical Fibers International (Vol. 45, pages 110 to 111, Published in April 1995), and Japanese Unexamined Patent Publication (Kokai) Nos. 9-3724, 8-173244 and 5-262862).
One of fibrous aspects in which the above-mentioned properties of PTT are maximally exhibited is a false-twist textured yarn. The false-twist textured yarn of PTT is excellent in elastic recovery and softness in comparison with the conventional false-twist textured yarn of PET or polybutylene terephthalate (hereinafter referred to as PBT) and is extremely suitable for a raw yarn of a stretchable material, as disclosed in Japanese Unexamined Patent Publication (kokai) Nos. 9-78373 and 11-093026.
When the PTT false-twist textured yarn is used while applying the above-mentioned properties thereof to various fields in which PET or polyamide fiber have been conventionally used, it is very important to facilitate the productivity of the PTT false-twist textured yarn and reduce the production cost thereof. However, since a drawn yarn produced through a two-stage process including the spinning and the drawing is used as a raw yarn to be subjected to the false-twist texturing process in such prior arts as disclosed in the above Publications, the productivity becomes lower to increase the production cost of the fiber. Also, since the drawn yarn is used as a raw yarn, it is impossible to apply thereto a draw false-twist texturing process which can be carried out at a high speed and a high productivity.
To facilitate the productivity and reduce the production cost, it is desirable to use a fiber produced through a single stage process similar to PET fiber or polyamide fiber and carry out the draw false-twist texturing at a high speed.
A technology for carrying out the draw false-twist texturing of PTT fiber produced through a single stage process is disclosed in Chemical Fibers International (Vol. 47, pages 72 to 74, published in February 1997) wherein a partially oriented yarn (hereinafter referred to as POY) of PTT is subjected to a draw false-twist texturing process. More specifically, PTT polymer having an intrinsic viscosity [xcex7] of 0.9 is extruded at a temperature in a range from 250 to 275xc2x0 C., cooled and solidified, and after being imparted with a finishing agent, taken up as POY of PTT (hereinafter referred to as PTT-POY) via a godet roll or no godet roll at a speed in a range from 600 to 3200 m/min, which is then subjected to a false-twist texturing process at a speed in a range from 450 to 1100 m/min.
Also, in Korean Unexamined Patent Publication No. 98049300, there is a description of a method for producing PTT-POY by spinning a polymer having an intrinsic viscosity in a range from 0.75 to 1.1 at a spinning speed in a range from 2500 to 5500 m/min and a technology for false-twist texturing this PTT-POY at a temperature in a range from 150 to 160xc2x0 C. and at a processing speed of 400 m/min. In Japanese Unexamined Patent Publication (Kokai) No. 57-193534, there is a description of PTT-POY obtained by spinning a polymer having an intrinsic viscosity [xcex7] of 0.97 at a spinning speed in a range from 2500 to 3000 m/min.
According to a study made by the present inventors, however, the PTT-POYs described in the above documents or Patent Publications have a drawback in that the yarn largely shrinks on a bobbin on which it is wound so as to tighten the bobbin, and if an amount of the yarn corresponding to that of PET fiber usually adopted in an industrial scale is wound, the bobbin largely deforms to prevent a cheese-shaped package from being removed from a spindle of a winder. Under the circumstances, even if the deformation of the bobbin could be mitigated by using a bobbin of a large mechanical strength, there would be a so-called bulge phenomenon in which opposite lateral sides of the package are swollen outward, or the yarn would be tightly wound in the inner layers. Accordingly, a yarn tension becomes higher and fluctuates largely when the yarn is unwound, and fluff and/or yarn breakage frequently occur during the draw false-twist texturing process, as well as irregularities of crimping or dying may be generated.
A technology for fixing a fibrous structure is disclosed in Japanese Examined Patent Publication (Kokoku) No. 63-42007, wherein a polymer prepared by blending PET with PTT and/or PBT is melted and extruded, which, after being cooled and solidified, is heat-treated by a hot roller and taken up at a speed of 3500 m/min or higher to result in a fiber having an elongation at break of 60% or lower and a shrinkage in boiling water of 7% or lower.
In this Publication, another fiber is disclosed as a comparative example, obtained from PTT homopolymer, and a polymer prepared by blending 10 wt % of PET with PTT homopolymer which is then heated at 180xc2x0 C. in the same manner as the above and taken up at a speed of 4000 m/min to have an elongation at break of 33% and a shrinkage in boiling water of approximately 4%. Also in this Publication, a high speed spinning in which the fiber is heated by a roller and PTT fiber obtained thereby are described. However, the technology disclosed in this Publication is one for suppressing the shrinkage by facilitating the crystallization of the resultant fiber when the fiber is used for clothing as it is so that the crepability is improved.
According to the study made by the present inventors, if the fiber is heat-treated at a temperature as high as 180xc2x0 C. or more, the bulge or collapse of yarn coils in the package may frequently occur. Also, since such a fiber is heat-treated at a high temperature to have a low elongation at break of 60% or lower which is similar to that of the drawn fiber, it is impossible to carry out the draw false-twist texturing of the fiber.
Regarding the polyamide type POY, Japanese Unexamined Patent Publication (Kokai) No. 50-71921 discloses the technology for obtaining a package free from the collapse of yarn coils by heat-treating the fiber with a hot roller. If the polyamide POY is not crystallized, it is liable to extend due to moisture absorption to cause the collapse of yarn coils. The technology disclosed in this Publication is to solve such a collapse of yarn coils.
In Japanese Unexamined Patent Publication (Kokai) No. 51-47114, a technology is disclosed wherein a fiber spun at a high speed is heat-treated under a tense state through a hot roller to crystallize the same, whereby the elongation at break of the fiber is lowered and the ease of false-twisting the fiber is improved. The technology disclosed in this Publication, however, aims to lower the elongation at break of the fiber and improve the crimpability thereof.
In other words, the technologies disclosed in both the Publications aim to achieve objects different from the improvement in package tightness due to fiber shrinkage, the restriction of bulge phenomenon and the suppression of change in fiber property with time, and therefore are useless with respect to the improvement in fiber shrinkage in a package or in the bulge generation of PTT fiber.
It has been thought, in the prior art, that, different from the polyamide type fiber, when the polyester type fiber is heated and crystallized so that the fibrous structure thereof is fixed, crystals disturb the movement of the fiber molecules to interfere with the smooth draw false-twist texturing process. Therefore, the technologies for heat-treating POY disclosed in the above Unexamined Patent Publications have not been applied to the polyester type fiber.
As described hereinabove, there is no PTT-POY free from the generation of fiber shrinkage and bulge in a package and capable of being subjected to the draw false-twist texturing process in a stable manner for a long period.
According to the study made by the present inventors, it was found that there are problems in the prior art PTT-POY and the production thereof as follows:
(A) A wound yarn shrinks to tighten a bobbin whereby it becomes impossible to remove a cheese-shaped yarn package from a spindle of a winder or a bulge may occur in the package. Accordingly, it is impossible to obtain a cheese-shaped package having the same amount of yarn as the industrially produced PET.
(B) Since physical properties of PTT-POY such as a shrinkage in boiling water or a peak value of thermal stress may vary even if it is stored at room temperature, it is impossible to industrially carry out the draw false-twist texturing; i.e., to produce the same quality false-twist textured yarn in a stable manner for a long period under the invariable condition without the generation of fluff or yarn breakage.
From the study of the reasons why the fiber shrinks as described above, the present inventors found that the following two items are decisive.
(1) Since PTT is of a zigzag molecular structure which is different from PET, a glass transition point (hereinafter referred to as Tg) is as low as 30 to 50xc2x0 C. and, if it is not crystallized as in a drawn yarn, the structure thereof is not fixed so that molecules are mobile even at a room temperature to result in shrinkage.
(2) Since the elastic recovery of PTT fiber is high, a stress caused by the winding remains as it is without being released.
In the above-mentioned prior art, there has been no suggestion at all that such a problem may occur.
According to the study made by the present inventors, physical properties of PET-POY hardly vary if it has been stocked at a room temperature. Contrarily, in PTT-POY disclosed in the above-mentioned prior art, physical properties such as a shrinkage in boiling water or a peak value of thermal stress may vary with time. Accordingly, it is impossible to industrially carry out the draw false-twist texturing; i.e., to produce the same quality false-twist textured yarn in a stable manner for a long period under the invariable condition without the generation of fluff or yarn breakage.
An object of the present invention is to provide a PTT fiber obtainable on an industrial scale and capable of being subjected to a draw false-twist texturing process in a stable state for a long period; i.e., PTT-POY, and a method for producing the same.
Problems to be solved for the purpose of achieving the object of the present invention are to obtain PTT-POY lower in package tightness and generation of bulge phenomenon caused by fiber shrinkage and capable of being produced on an industrial scale as a countermeasure to the above-mentioned (A), and to obtain PTT-POY free from change in physical properties with time at a room temperature and capable of being subjected to a draw false-twist texturing process on an industrial scale as a countermeasure to the above-mentioned (B).
To solve the above problems, the present inventors have diligently studied and found that the generation of package tightness and the bulge phenomenon, which are decisive problems during the production of PTT-POY, caused by the fiber shrinkage is surprisingly avoidable, if the fiber has a specific range of orientation and crystallinity. Also, the inventors have found that such a fiber is favorably produced by a specific spinning method wherein the fiber is heat-treated and crystallized under a special condition and wound at an extremely low tension.
Further surprisingly, it has been found that, different from PET fiber, the fiber having the orientation and crystallinity in a range defined according to the present invention is capable of being subjected to a draw false-twist texturing process to result in a false-twist textured yarn excellent in quality grade even if it is heat-treated to be crystallized. Furthermore, since the fiber structure of PTT according to the present invention is fixed due to the crystallization, the physical properties thereof hardly vary with time, whereby it is possible to produce a false-twist textured yarn having the same quality grade in a stable state without the generation of fluff and yarn breakage.
That is, the present invention is as follows:
1. A polytrimethylene terephthalate fiber composed of 90 mol % or more of trimethylene terephthalate repeating units and satisfying the following conditions defined in (A) to (E):
(A) a density is in a range from 1.320 to 1.340 g/cm3 
(B) a birefringence is in a range from 0.030 to 0.070
(C) a peak value of thermal stress is in a range from 0.01 to 0.12 cN/dtex
(D) a shrinkage in boiling water is in a range from 3 to 40%, and
(E) an elongation at break is in a range from 40 to 140%.
2. A PTT fiber as defined by above item 1, wherein an intensity of a wide angle X-ray diffraction in the direction vertical to a fiber axis satisfies the following equation:
I1/I2xe2x89xa71.0
xe2x80x83wherein I1 is a maximum diffraction intensity defined at 2xcex8=15.5 to 16.5 degrees, and I2 is a mean diffraction intensity defined at 2xcex8=18 to 19 degrees.
3. A PTT fiber as defined by above items 1 or 2, wherein an oil satisfying the following conditions defined in (P) to (S) is adhered to the fiber in a range from 0.2 to 3 wt %:
(P) the content of one kind or more of nonionic surfactants is in a range from 5 to 50 wt %, selected from compounds in which alcohol having 4 to 30 carbon atoms is added with ethylene oxide or propylene oxide;
(Q) the content of ionic surfactant is in a range from 1 to 8 wt %;
(R) one kind or more of fatty ester having a molecular weight in a range from 300 to 700 and/or one kind or more of polyether represented by the following formula (referred to as polyether-1) are contained; in the polyether-1, ethylene oxide unit and propylene oxide unit are copolymerized with each other so that a mass ratio of [propylene oxide unit]/[ethylene oxide unit] is in a range 20/80 to 70/30 and a molecular weight is in a range from 1300 to 3000, wherein a total of contents of the fatty ester and the polyether-1 is in a range from 40 to 70 wt %:
R1xe2x80x94Oxe2x80x94(CH2CH2O)n1xe2x80x94(CH(CH3)CH2O)n2xe2x80x94R2
xe2x80x83(wherein R1, R2 represent a hydrogen atom or an organic group having the number of carbons in a range from 1 to 50, and n1, n2 are an integer in a range from 1 to 50); and
(S) the content of polyether represented by the following formula (referred to as polyether 2) is 10 wt % or less, in which ethylene oxide unit and propylene oxide unit are copolymerized with each other so that a mass ratio of [propylene oxide unit]/[ethylene oxide unit] is in a range 20/80 to 80/20 and a molecular weight is in a range from 5000 to 50000:
xe2x80x83R3xe2x80x94Oxe2x80x94(CH2CH2O)n1xe2x80x94(CH(CH3)CH2O)n2xe2x80x94R4
xe2x80x83(wherein R3, R4 represent a hydrogen atom or an organic group having the number of carbons in a range from 1 to 50, and n1, n2 are each an integer in a range from 50 to 1000).
4. A PTT fiber as defined by any one of above items 1 to 3, wherein a coefficient G of static friction corrected by a fiber size is in a range from 0.06 to 0.25; the coefficient G is calculated from a coefficient F/Fxcexcs of fiber-fiber static friction and a total fiber size d (dtex), as is represented by the following equation (1):
G=(F/Fxcexcs)xe2x88x920.00383xc3x97dxe2x80x83xe2x80x83(1)
5. A PTT fiber as defined by above item 4, wherein a coefficient F/Mxcexcd of dynamic friction between fiber and metal is in a range from 0.15 to 0.30.
6. A PTT fiber as defined by any one of above items 1 to 5, wherein the following conditions defined in (F) and (G) are satisfied:
(F) the content of titanium oxide having an average particle size in a range from 0.01 to 2 xcexcm is in a range from 0.01 to 3 wt %, and the number of aggregates of the titanium oxide particles having the longest length exceeding 5 xcexcm is 12/mg of fiber or less; and
(G) the fiber has U % in a range from 0 to 2%.
7. A PTT fiber composed of 90 mol % or more of trimethylene terephthalate repeating units, satisfying the following conditions defined in (H) to (K), and wound to form a cheese-shaped package:
(H) a birefringence is in a range from 0.030 to 0.070
(I) a peak value of thermal stress is in a range from 0.01 to 0.12 cN/dtex
(J) an intensity of a wide angle X-ray diffraction in the direction vertical to a fiber axis satisfies the following equation:
I1/I2xe2x89xa71.0
xe2x80x83wherein I1 is a maximum diffraction intensity defined by 2xcex8=15.5 to 16.5 degrees, and I2 is a mean diffraction intensity defined by 2xcex8=18 to 19 degrees; and
(K) a relaxed shrinkage is in a range from 0 to 3%.
8. A cheese-shaped package formed of the PTT fiber defined by any one of above items 1 to 7, wherein a bulging percentage is 20% or less.
9. A cheese-shaped package as defined by above item 8, wherein the released shrinkage of the PTT fiber wound thereon is in a range from 0 to 3%.
10. A cheese-shaped package as defined by above items 8 or 9, wherein a width within which the PTT fiber is wound on a bobbin is in a range from 40 to 300 mm and a weight of the PTT fiber wound on the bobbin is 2 kg or more.
11. A method for producing a PTT fiber by melt-spinning PTT composed of 90 mol % or more of trimethylene terephthalate repeating units, wherein a melted multifilamentary yarn extruded from a spinneret is quickly cooled to be a solidified multifilamentary yarn which, after being heated to a temperature in a range from 50 to 170xc2x0 C., is then wound on a bobbin at a winding tension in a range from 0.02 to 0.20 cN/dtex and a speed in a range from 2000 to 4000 m/min.
12. A method for producing a PTT fiber, as defined by above item 11, wherein after the melted multifilamentary yarn extruded from the spinneret has been quickly cooled to be the solidified multifilamentary yarn, an oil is imparted to the multifilamentary yarn before being wound on the bobbin at a pickup in a range from 0.2 to 3 wt % relative to the multifilamentary yarn.
13. A method for producing a PTT fiber as defined by above item 12, wherein the oil satisfying the following conditions defined by (P) to (S) is imparted:
(P) the content of one kind or more of a nonionic surfactant is in a range from 5 to 50 wt %, which surfactant is selected from compounds composed of alcohol having the number of carbons in a range from 4 to 30 added with ethylene oxide or propylene oxide;
(Q) the content of an ionic surfactant is in a range from 1 to 8 wt %;
(R) one kind or more of fatty ester having a molecular weight in a range from 300 to 700 and/or one kind or more of polyether represented by the following formula (referred to as polyether-1) are contained, in the polyether-1, ethylene oxide unit and propylene oxide unit are copolymerized with each other so that a mass ratio of [propylene oxide unit]/[ethylene oxide unit] is in a range 20/80 to 70/30 and a molecular weight is in a range from 1300 to 3000, wherein a total of contents of the fatty ester and the polyether-1 is in a range from 40 to 70 wt %:
R1xe2x80x94Oxe2x80x94(CH2CH2O)n1xe2x80x94(CH(CH3)CH2O)n2xe2x80x94R2
xe2x80x83(wherein R1, R2 represent a hydrogen atom or an organic group having the number of carbons in a range from 1 to 50, and n1, n2 are each an integer in a range from 1 to 50); and
(S) the content of polyether represented by the following formula (referred to as polyether-2) is 10 wt % or less, in which ethylene oxide unit and propylene oxide unit are copolymerized with each other so that a mass ratio of [propylene oxide unit]/[ethylene oxide unit] is in a range from 20/80 to 80/20 and a molecular weight is in a range from 5000 to 50000:
R3xe2x80x94Oxe2x80x94(CH2CH2O)n1xe2x80x94(CH(CH3)CH3O)n2xe2x80x94R4
xe2x80x83(wherein R3, R4 represent a hydrogen atom or an organic group having the number of carbons in a range from 1 to 50, and n1, n2 are each an integer in a range from 50 to 1000).
14. A method for producing a PTT fiber as defined by any one of above items 11 to 13, wherein the fiber is imparted with an oil by an aqueous emulsion of a concentration in a range from 2 to 10 wt %.
15. A method for producing a PTT fiber as defined by any one of above items 11 to 14, wherein a polymer satisfying the following condition defined in (L) is extruded from the spinneret so that a draft during the spinning process is in a range from 60 to 2000:
(L) the content of titanium oxide having an average particle size in a range from 0.01 to 2 xcexcm is in a range from 0.01 to 3 wt %, and the number of aggregates of the titanium oxide particles having the longest length exceeding 5 xcexcm is 25/mg of polymer or less.
16. A false-twist textured yarn formed of a PTT fiber as defined by any one of above items 1 to 7.
17. A false-twist textured yarn formed of a PTT fiber composed of 90 mol % or more of trimethylene terephthalate repeating units and satisfying the following conditions defined in (M) to (O):
(M) a crimp elongation is in a range from 150 to 300%;
(N) the number of crimps is in a range from 4 to 30/cm; and
(O) the number of snarls is in a range from 0 to 3/cm.
18. A false-twist textured yarn as defined by above item 17, wherein the number of crimps is in a range from 8 to 25/cm.
19. A false-twist textured yarn as defined by any one of above items 16 to 18, wherein the following condition defined in (K) is satisfied:
(K) the content of titanium oxide having an average particle size in a range from 0.01 to 2 xcexcm is in a range from 0.01 to 3 wt %, and the number of aggregates of the titanium oxide particles having the longest length exceeding 5 xcexcm is 12/mg of fiber or less.
20. A false-twist textured yarn as defined by any one of above items 16 to 19, wherein an oil containing fatty ester having a molecular weight in a range from 300 to 800 and/or mineral oil having a Redwood viscosity at 30xc2x0 C. in a range from 20 to 100 seconds is adhered to the false-twist textured yarn at a pickup in a range from 0.5 to 5 wt % relative to the false-twist textured yarn.
21. A false-twist textured yarn package, wherein the false-twist textured yarn defined by any one of above items 16 to 20 is wound on a bobbin.
22. A false-twist textured yarn package as defined by above item 21, wherein a hardness of the package is in a range from 70 to 90 and a winding density is in a range from 0.6 to 1.0 g/cm3.
23. A method for producing a false-twist textured yarn, wherein the PTT fiber as defined by any one of above items 1 to 7 is subjected to a draw false-twist texturing process.
24. A method for producing a false-twist textured yarn, wherein the cheese-shaped package as defined by any one of above items 8 to 10 is subjected to a draw false-twist texturing process.
25. A fabric wherein the false-twist textured yarn as defined by any one of above items 16 to 20 is used as part or all thereof.